An Intro to Quantum Computing

Image: Daan Botlek

1. Andrew Lee

When I first started working in quantum computing two and a half years ago, people would often ask me, “What is quantum computing?”. Things have changed a lot since then. People still ask what quantum computing is, but more and more it feels like they ask because they’re genuinely curious and not simply trying to be polite.

I think much of that curiosity is attributable to the fact that quantum computing is becoming more prominent in the media. It’s hard to browse the news these days without coming across mentions of the technology. Companies like Google, IBM, Microsoft and a handful of startups around the world are all vying to develop the technology. The promise of incredible processing power and the ability to solve previously intractable problems is capturing a growing amount of attention. But what is it, and what will it let us do?

2. What is quantum computing?

While it can be difficult to answer this question in a way that’s accurate yet intuitive, I’ve found it’s helpful to start by looking at classical computing.

In classical, or non-quantum, computers (like the kind of computer you’re reading this article on), the basic unit of information is the bit, or binary digit. A bit can hold one of two values (typically represented by 0 and 1) and can be represented using any two-state system. In older computers, these may have been a physical lever that could be in one of two positions or the absence or presence of a hole in a punch card. In more modern times, bits have been represented using microscopic switches that are on or off.

In quantum computers, the basic unit of information is the qubit, or quantum bit. Like a bit, a qubit can be represented using a two-state system. Unlike a bit, however, the systems used to represent qubits are subject to quantum mechanical phenomena. These are phenomena that become noticeable at the scale of atoms and subatomic particles. Examples of systems that can be used to represent qubits include trapped ions or small superconducting circuits.

Quantum mechanical phenomena relevant to quantum computing include superposition, which can allow qubits to represent both 0 and 1 simultaneously (as opposed to a bit, which can represent only one of 0 or 1 at a time), and entanglement, which can allow the value of one qubit to instantaneously inform us about the value of another qubit. The key takeaway of all this is that quantum mechanical phenomena may allow quantum computers to perform certain tasks significantly faster than classical computers are able to.

3. Why should we care about quantum computing?

When people say quantum computers may be able to perform certain tasks significantly faster than classical computers are able to, they mean significantly faster. For example, there are certain kinds of tasks or problems, such as simulating large molecules with high fidelity, that would take a classical computer years to solve. In theory, quantum computers have the potential to solve these kinds of problems on timescales that are immensely shorter.

This could have a major impact on many industries. There are problems in finance, energy, the life sciences, materials science, logistics, and others that simply cannot be solved optimally (i.e. the best possible solution cannot be found) in reasonable amounts of time using classical computers. Thus, today we use solutions that are “good enough” for many of these problems. And while using solutions that are “good enough” is acceptable for many problems, there are some problems for which obtaining exact or near exact solutions has the potential to have significant impacts on society.

For example, let’s revisit the problem of simulating large molecules with high fidelity. If we’re able to perform these simulations using quantum computers, this may allow us to more efficiently design new drugs or new materials with specific properties, such as materials that allow us to build lighter and more efficient batteries. It’s not hard to imagine the positive effect breakthroughs like these could have.

4. How long will it be until quantum computers get here?

While the answer to this can depend largely on whom you ask, there appears to be a general consensus forming in the industry that we might have hardware powerful enough for commercial applications within the decade. There are still a number of challenges that need to be overcome before we get to this point, however.

Qubits are very fragile and keeping them in a condition where they can be used to perform calculations is very difficult. This, among other challenges, makes scaling up the hardware a difficult task. We’re making progress, though. More and more resources are being dedicated to developing quantum hardware and companies and organizations around the world are announcing new breakthroughs in quantum hardware every few months.

Another barrier is building the algorithms and software to run on these devices. While this doesn’t get as much attention in the media, it’s just as important. Similar to how specialised classical software is needed to address complex problems using classical computers, solving problems using quantum hardware requires highly specialised software. Here, too, progress is being made; companies like 1QBit are exploring today how quantum software can be used to address some of the largest challenges faced by some of the world’s largest companies.

5. Is there anything we can start doing now?

There’s still a ways to go before the technology is meaningfully commercialized. That being said, it may be useful to start learning more about quantum computing now so you can start thinking about how the technology might be applied and what impact it could have on your business. Quantum computing has the potential to enable many new, radical applications and revolutionise industries. If we’ve learned anything from past technological revolutions, it’s that it doesn’t hurt to think ahead.

About the author

Andrew is an analyst at 1QBit, the Vancouver-based company that builds quantum and quantum-inspired software. Prior to joining 1QBit, he worked with a variety of organisations, including a boutique investment bank, Statistics Canada, and an academic research lab specialising in metal organic frameworks. Andrew recently graduated with distinction from the University of British Columbia with a BSc in Statistics and Economics.